Photographic carbon tissue



April 1, 1952 J. F. HANSMAN ET AL 2,590,857

PHOTOGRAPHIQ CARBON TISSUE Filed Sept. 10, 1945 reduces the sharpness.

Patented Apr. 1, 1952 UN ITED PHOTOGRAPHIC CARBON TISSUE John F..Hansmanand Melvin J. Jurisch, Chicago, 111.; said Hansman assignor to saidJuriscli Application September 10,1945, Serial No. 615,507

(01. Nib-128.2)

11' Claims. 1

This invention relates to photographic carbon tissue and moreparticularly to a method of employing the same in the manufacture ofphotographic silkscreen.

Photographic carbon tissue comprises a fibrous backing material which isprovided with a photosensitive or photosensitizable surface of gelatinor other, colloid adhering to the backing. Normally the paper issensitized with a bichromate and on account of the effect of thebichromate on thegelatin, the sheets are normally sensitized shortlybefore use. For thatreason the paper is normally sold in an unsensitizedform.

In employing the carbon tissue in silk screen work,v the carbon tissueis first sensitized in a bichromate solution and exposed to animagewhile in contact with a photographic negative or positive; Light actingupon the sensitized gelatin renders those portions insoluble which areexposed to it, while the protected areas remain soluble in warm water.The exposed sheet is thenapplied to a silk screen.

There were two general methods in use for supporting the tissueduringexposure to an image. Invthem the carbon tissue, is supported, as,for; example, on a thin sheet of Celluloid or a varnished negative. Thewet sensitized carbon tissue is squeegeed to the wax surface of theCelluloid or varnished surface of the negative and it may be exposed tothe light while so supported. After exposure, it is placed in warm waterand the paper backing stripped away. Thereafter the soluble areas werewashed away. Because of. thewet swollen condition ofthe gelatinand.thelack of close and intimate contact between the sensitized surface andthe. negative or: the Celluloid, there was a. loss of sharpness. Ifasupportwas used a thickness of the support Likewise light does notpenetrate as well into the swollen gelatin. Exposure must be greatlyincreased because of the diminished sensitiveness of the wet film. Thereis also a tendency of a gelatin film to frill and reticulate during thewarm water development owing to lack of adhesion to the wet film and thewax surface.

An embodiment of a photographic carbon tissue made in accordance withthis invention is illustrated in the accompanying drawing, in which:

Fig; 1 is a plan view of a photographic carbon tissue illustrating thevarious layers composing the. tissue; and

Fig. 2 is a vertical cross section of the tissue shown in Fig. 1.

As contrasted with the wet processes heretofore employed, the presentinvention makes it possible to employ either a. dry or damp process inwhich the-sensitized gelatin is either dry or only slightly moist. Thisis accomplished by applying to the surface of the gelatin I l on thecarbon tissue a thin transparent coating or film l2, preferably of a waxadherent material. Themeferred film is produced by the application of aweak solution of collodion. Such a film I2 is porous or permeable toliquid solutions and particularly to liquid solutions incorporating abichromate. During storage the film l2 protects the gelatin l I frommechanical and possibly from chemical deterioration, and it does notmaterially interfere with sensitization. For example, the use of thefilm hereinafter described permits sensitization of the underlyinggelatin by immersion for 3 minutes in a 4% solution of bichromate inwater at a temperature of F. After sensitization the sensitized tissuemay be dried and then applied directly to the negative or to a waxsupport if desired. The film has great adherence and, therefore, avoidsthe dificulties due to lack of adherence of the gelatin. At the sametime it is not necessary to have the gelatin in wet form during theexposure, and the difficulties due to wetting of the gelatin may beavoided.

The followingis an example of the preferred film. A carbon tissue m ofusual form comprising an. opaque fibrous backing of paper, havingasurface coated withnon-sensitized-gelatin I I, is treated withasolutionby weight of:

1O9.4 parts-a1cohol 109.4 parts ether 1.2 parts gun cotton 1 partglycerine Thisv solution is spread over. the surface of the gelatin inany suitable manner, drained, and then permitted to dry thereon, thusproducing a very thin nitrocellulose film. The glycerine is employed torender the film porous or permeable to liquid. Diethylene glycol willalso serve the same purpose. While the chemical action of the glycerineis not thoroughly understood, it is believed to act as a hydrophilicmaterial within the normally hydrophobic nitrocellulose wherebypermeability to water is produced.

The dried film is normally marketed with the gelatin unsensitized. Whenit comes time to use the tissue, it is immersed in a sensitizingsolution such as a 4% solution of bichromate in water. Three minutes at65 F. will serve to sensitize gelatin beneath the film here described.Thereafter the surplus sensitizer is drained off and the tissue may behung up to dry or it may be squeegeed to a highly polished plate. Whenhung up to dry it should not be used until the film surface is dry tothe touch. When dried on a polished plate it should not be strippeduntil a small corner has been lifted and found dry to the touch. Whenthe surface is dry the sheet will remove easily from the plate.

' If" desired, to reduce any overmoistness of the gelatin a smallquantity of talcum powder may be dusted over'the entire film surfacewith a soft brush.

' The dried tissue is then placed in contact with a. photographicnegative. or positive, the emulsicns: of each. facing each. other. Thetime of.

exposure depends upon the type of equipment and is no part of thisinvention. A reasonable example would be 7 to 10 minutes at 5 feet witha 35-ampere arc light. After exposure the film is dipped for severalseconds in a cool water bath and is then squeegeed to a temporarydeveloping support which has been polished with a tacky wax. It isallowed to stand for a few minutes and is then placed in hot water atabout 100 F. until the paper back has softened sufficiently to permitthe paper back to be peeled off. This usually takes about or minutes.

The soluble gelatin is then washed out until the image alone remains,after which the plate is rinsed in cold water and drained and placedunder a black silk screen, with the screen in contact with the residualgelatin. The gelatin is then dried while in contact with the silk andbecomes adherent thereto. The silk with the gelatin is then strippedfrom the support and any residual porous film may be removed with asuitable solvent, such as ether or a combination of alcohol and ether.

The foregoing detailed description has been given for clearness ofunderstanding only, and no unnecesary limitations should be understoodtherefrom.

What we claim as new, and desire to secure by Letters Patent, is:

1. The method which comprises providing a carbon tissue with a facialfilm of a water-insoluble transparent material containing a minorproportion of a hydrophilic material and an intermediate layer of awater-soluble colloid, sensitizing the tissue in an aqueous bathcontaining a sensitizing agent through the film, drying the tissue,exposing the tissue to an image, placing the film side of the tissue inadherent contact with a rigid support, removing the backing and surpluscolloid from the tissue While on said support and while held by saidfilm, then bringing a silk screen into adherent contact with the colloidwhile the material is still on the support, and finally stripping offthe film.

2. The method as set forth in claim 1, in which the film is cellulosenitrate.

3. The method as set forth in claim 1, in which the film contains asmall proportion of a polyhydric alcohol.

4. The method as set forth in claim 1, in which the colloid is gelatinand the sensitizer is a bichromate.

5. The method which comprises providing a carbon tissue comprising abacking of an opaque fibrous material and a thin layer of anunsensitized soluble colloid thereon capable of being sensitized with alight-sensitizing agent, covering the face of the colloid with a thinadherent film of a wax-adherent material permeable to thelight-sensitizing agent, sensitizing the colloid through the film,exposing the sensitized colloid to an image through the film, applyingthe film side of the colloid and backing to a waxed surface, andstripping off the backing while the film is adhered to the waxed surfaceand the colloid is adhered to the film.

6. The method which comprises providing a carbon tissue comprising abacking of an opaque fibrous material and a thin layer of anunsensitized soluble colloid thereon capable of being sensitized with alight-sensitizing agent, covering the face of the colloid with a thinadherent -film of a wax-adherent material permeable to thelight-sensitizing agent,.sensitizing the colloid through the film byapplying a solution of a light-sensitizing agent, substantially dryingthe carbon tissue and film, exposing the sensitized colloid to an imagethrough the film, applying the film side of the colloid and backing to awaxed surface, and stripping off the backing while the film is adheredto the waxed surface and the colloid is adhered to the film.

7. The method which comprises providing a carbon tissue comprising abacking of an opaque fibrous material and a thin layer of unsensitizedgelatin, covering the face of the gelatin with a thin layer comprisingessentially nitrocellulose, sensitizing the colloid through the film byapplying an aqueous solution of a water-soluble bichromate,substantially drying the carbon tissue and film, exposing the gelatin toan image through the film, applying the film side of the carbon tissueto a waxed surface, immersing the composite structure in water, removingthe fibrous backing and washing out the soluble gelatin in the water,transferring the gelatin side to a silk screen, and stripping off thefilm.

8. A photographic carbon tissue comprising superposed layers consistingof an opaque fibrous backing, an unsensitized water soluble colloidalcoating on the backing, and a thin porous film containing approximatelyequal amounts of nitrocellulose and glycerine on the surface of thecolloid, said backing and film being adherent to the colloid but capableof being stirpped therefrom.

9. A photographic carbon tissue comprising an opaque fibrous backing, anunsensitized water soluble colloidal coating superposed on the backing,and a thin porous film containing approximately equal amounts ofnitrocellulose and a material of the class consisting of glycerine anddiethylene glycol on the surface of the colloid.

10. A photographic carbon tissue comprising an opaque fibrous backing,an unsensitized water soluble colloidal coating on the backing, and athin porous film containing approximately equal amounts ofnitrocellulose and a polyhydroxy a1- cohol on the surface of thecolloid.

11. A photographic carbon tissue comprising superposed layers consistingof a fibrous backing, an unsensitized coating comprising gelatin on thebacking, and a thin porous film containing approximately equal amountsof nitrocellulose and a material of the class consisting of glycerineand diethylene glycol on the surface of the coating.

JOHN F. HANSMAN. MELVIN J. JURISCH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,327,931 Waters Jan. 13, 19201,640,815 Eggiman et al Aug. 23, 1927 1,804,555 Gentile May 12, 19311,915,873 Spencer June 27, 1933 1,942,872 Murray Jan. 9, 1934 2,030,731Young Feb. 11, 1936 2,121,205 Lippert June 21, 1938 2,326,058 'NadeauAug. 3, 1943 2,337,012 Bjeig et al Dec. 14', 1943 2,367,420 Mullen Jan.16, 1945 FOREIGN PATENTS Number Country Date 201,241 Great Britain Aug.2, 1923

1. THE METHOD WHICH COMPRISES PROVIDING A CARBON TISSUE WITH A FACIALFILM OF A WATER-INSOLUBLE TRANSPARENT MATERIAL CONTAINING A MINORPROPORTION OF A HYDROPHILIC MATERIAL AND AN INTERMEDIATE LAYER OF AWATER-SOLUBLE COLLOID, SENSITIZING, THE TISSUE IN AN AQUEOUS BATHCONTAINING A SENSITIZING AGENT THROUGH THE FILM, DRYING THE TISSUE,EXPOSING THE TISSUE TO AN IMAGE, PLACING THE FILM SIDE OF THE TISSUE INADHERENT CONTACT WITH A RIGID SUPPORT, REMOVING THE BACKING AND SURPLUSCOLLOID FROM THE TISSUE WHILE ON SAID SUPPORT AND WHILE HELD BY SAIDFILM, THEN BRINGING A SILK SCREEN INTO ADHERENT CONTACT WITH THE COLLOIDWHILE THE MATERIAL IS STILL ON THE SUPPORT, AND FINALLY STRIPPING OFFTHE FILM.
 11. A PHOTOGRAPHIC CARBON TISSUE COMPRISING SUPERPOSED LAYERSCONSISTING OF A FIBROUS BACKING, AN UNSENSITIZED COATING COMPRISINGGELATIN ON THE BACKING, AND A THIN POROUS FILM CONTAINING APPROXIMATELYEQUAL AMOUNTS OF NITROCELLULOSE AND A MATERIAL OF THE CLASS CONSISTINGOF GLYCERINE AND DIETHYLENE GLYCOL ON THE SURFACE OF THE COATING.